Uniaxial compressive behavior study of normal-strength concrete using waste steel slag aggregate through laboratory tests and numerical simulation

Steel slag aggregate concrete (SSAC) is a potentially sustainable construction material. But at present, the lack of a uniaxial compression stress-strain model of SSAC has prevented engineers from designing structural components well. Furthermore, a mesoscopic numerical model to predict the uniaxial compressive behavior of SSAC is lacking. Given the current research gaps, the present study conducted uniaxial compressive load tests on SSAC cylinder specimens of C30, C40, and C50 strength grades and 0 %, 50 %, and 100 % steel slag aggregate (SSA) replacement ratios. The SSAC cylinders have a similar failure pattern to the reference concrete specimens prepared with natural aggregate (NAC). Based on the laboratory test results, a modified uniaxial compression stress-strain model of SSAC was proposed to incorporate changes in concrete strength grades and SSA replacement ratios. The stress-strain curves of SSAC exhibited a longer ascending branch, a larger elastic modulus, and a higher peak stress than NAC. The increment in peak stress increased as the concrete strength grade increased, while the increment in elastic modulus decreased as the concrete strength grade increased. The quantitative relationships between peak stress, peak strain, elastic modulus, and SSA replacement ratio were established, which were in agreement with the experimental values. However, the stress-strain curves of SSAC showed a steeper descending branch, and the compressive toughness of C40 and C50 concrete decreased with an increase in the SSA replacement ratio. This indicates the poor ductility of SSAC. In addition, this study established the mesoscopic numerical model of SSAC based on the laboratory test results. For C30, C40, and C50 concrete, the cohesive strength (including tensile strength and fracture energy) of the interfacial transition zone (ITZ) around SSA must be 125 %, 150 %, and 175 % higher than the ITZ around NA. The simulation results indicated that with the increase of the aggregate volume content and maximum particle size, SSA can improve the mechanical properties of concrete more significantly.